Kinetic and structural data have revealed that chymotrypsin possesses an active site which is ionic. The reason for undertaking this research project is to investigate the electrostatic properties of the site. This will be accomplished by studying the ionic strength and dielectric effects on chymotrypsin-catalyzed hydrolyses. Since the ionic form of the site is pH dependent, the work will be done over a wide pH range using a variety of substrates, i.e., peptides, esters and amides. The functional ionic groups will be identified and characterized by studying the influence of ionic strngth, dielectric, and temperature on their pKa values. This will be accomplished by systematically investigating chemically modified chymotrypsins using amino acid sequence analysis and Fourier transform infrared spectroscopy. The extent to which the active sites of chymotrypsin is exposed to solvent has become highly controversial. The absolute assignment of the kinetic pKa values to the ionic groups responsible for catalytic activity depends upon the extent of solvent interaction. Therefore, studies which determine the influence that changes in ionic strength and dielectric effects of the solvent have on these pKa values are an important contribution to understanding the mechanism of chymotrypsin catalysis.